This invention relates to stepping motors and more particularly to a method and drive circuitry for providing increased torque or speed with a minimum increase in power consumption.
Stepping motors are conventionally operated in one of two modes. Single phase operation involves exciting or energizing one of the windings (or phases) of the motor at a time, and stepping is accomplished by sequentially energizing adjacent phases. The alternative mode of operation is dual phase excitation in which two adjacent phases are energized at all times; in the dual phase operation one phase continues to produce torque throughout the first half of the next phase excitation so that maximum performances (torque) from a given size motor is achieved, but this is accomplished only at the expense of excessive power consumption. Thus while the single phase excitation consumes less power, more torque is produced by the dual phase excitation.
While high torque characteristics are of course desirable, it is of increasing importance to prevent unnecessary power consumption. Accordingly, it is the object of the present invention to provide improved stepping motor operation, and in particular to tailor the torque-speed characteristic of the stepping motor to the application while minimizing the power consumption.
It is a further object of the present invention to provide an improved stepping motor drive circuit which satisfies these requirements.
It is a still further object of the present invention to provide a stepping motor with efficient performance, especially to tailor the motor torque characteristics to the dynamic load requirements while minimizing the power supply requirements.